Trucks are well known devices having numerous references in the art. Conventional skateboards and roller skates are equipped with steering mechanisms known as trucks. The main body of the truck is generally formed by placing the axle, onto which the wheels will be rotatably attached, into the mold when the truck is cast so as to bond the two metals into one piece. Thus once the axle becomes damaged in any way; this necessitates the replacement of the entire truck.
Additionally, conventional trucks follow a basic design in which an axle pivots about an arm attached at one end to the center portion of the axle. The other end of this pivot arm is loosely fitted, at an angle of approximately 45 degrees, into a plastic cup mounted in a baseplate, thus forming a ball-like joint. A pair of doughnut-shaped grommets, usually made of rubber or urethane plastic of various hardnesses, is mounted on a substantially vertical kingpin fixed in the baseplate on the side of the axle opposite the plastic cup. These grommets grasp a ring extending from the axle body so that the axle is suspended between the ball-like joint and the grommets. By adjusting the kingpin, the tension on the grommets may be increased or decreased, thereby varying the balance between turning stability and turning ease. The kingpin employed in conventional trucks is oriented at a substantially right angle to the tilting movement of the deck, resulting in high stress on the kingpin. Because the kingpin and the grommets do not adequately stabilize the pivot arm axis, and because of the loose fit between the pivot arm and the plastic cup, the angle of the pivot axis tends to deteriorate as the axle tilts, so that very tight turns may be difficult or impossible to achieve.
A further drawback of this standard design is that the suspension system formed by the plastic grommets fails to provide fine steering control. Riders control the angle of the deck's tilt, and thus the size of the turns they make, by varying the distance by which they shift their weight laterally across the width of the deck. Regardless of their hardness or of how they are adjusted, the standard urethane grommets do not offer a regular, orderly pattern of resistance to such weight shifts. The result is that the riders cannot easily predict or measure how far they must shift their weight to achieve steering radii of various sizes.
Moreover, when a rider removes his weight from the side of the deck at the end of a turn, the plastic grommets used in conventional trucks do not return the vehicle to the neutral, non-turning position quickly enough. Sideward shifts of a rider's body mass create forces, which compress the grommets, thus causing the deck to tilt arid the vehicle to steer. Conventional trucks behave like dampers in the sense that the energy used to compress the grommets is largely dissipated; the grommets retain very little of this energy for use in quickly rebounding the axles to the straight-ahead position. This is especially noticeable, and troublesome, when the rider attempts to propel and accelerate himself by means of quick, alternating turns. High-performance riding depends upon the ability of the trucks to quickly resume straight-forward motion after the rider discontinues a lateral weight shift.
Additionally, conventional trucks often begin to feel kinked, as if they "want" to steer in one direction more than the other, such as to the left more than to the right. The plastic cup in which the axle pivot arm swivels, and the urethane grommets, tend to permanently deform in an asymmetrical manner in accordance with the rider's steering habits and may oppose his attempts to steer the vehicle either straight ahead or against the memory of the plastic cup and grommets.
Various prior patent arts have used springs or alternate axle configurations to allow for adequate steering control. Progression to the use of the current standard with the plastic cup and grommets was a logical step, but still does not have the consistency or precision necessary for high performance acrobatic maneuvers.